Semiconductor processing typically involves fabrication of devices, such as transistors, diodes, and integrated circuits, upon a thin piece of semiconductor material called a substrate. The semiconductor processing takes place in a reaction region, where gases are passed over the substrate, resulting in a controlled deposit of material upon the substrate. The substrate is lifted into the reaction region by a susceptor.
A gap is formed between the susceptor and a baseplate of the reaction region during processing. The purpose of the gap is to allow fluid communication between the inside of the reaction region and outside the susceptor. With the gap, extraneous gas containing the reactive material can exit the reaction region. In addition, the gap is used to control the flow of gas into or out of the reaction region in a controlled and uniform manner.
In addition, the gap is necessary as direct physical contact between the susceptor and the baseplate could result in particle generation. The direct physical contact results in the release of particles from either the susceptor or the baseplate. Particle generation is problematic as the smallest particles can contaminate and potentially cause defects in the processed substrate.
A uniform gap between the susceptor and the baseplate has been desired to avoid issues of particle generation. In addition, a uniform gap will keep the gas flow into or out of a reactor chamber uniform around the entire seal. Prior art approaches to semiconductor processing have utilized pads disposed between the susceptor and the baseplate in order to maintain a uniform gap. The pads prevent direct physical contact between the susceptor and the baseplate. The height of the pads can range between 0.001 inches (approximately 25 μm) and about 0.05 inches (approximately 1275 μm).
Over time, continued processing can lead to a deposit of reactive materials on and around the pads of the susceptor. This deposition build-up can lead to the reduction in size of the gap between the susceptor and the baseplate. Similar to the particle generation, a deposition build-up can cause issues of contamination and defects in the processed substrate. Thus, it is desired to have a uniform gap between the susceptor and the baseplate arranged without the deposition build-up of reactive materials and the particle generation.